Wednesday 29 September 2010 20.06 EDT
First published on Wednesday 29 September 2010 20.06 EDT

Parents of hyperactive children should not be blamed for failing to bring up their offspring properly, according to scientists who today publish evidence that the condition is genetic.

Children with attention deficit hyperactivity disorder (ADHD) find it hard to concentrate and can be wild and uncontrollable both at home and at school. Controversy has raged around the drug most widely used to calm such children, Ritalin, which is of the amphetamine family. In the US, such drugs became popular among families who wanted their lively (non-ADHD) boys to do better in class, while in the UK they were tagged chemical coshes. Meanwhile, parents have often tacitly been blamed for lack of discipline or giving their children a sugar and additive-laden diet.

And the particular DNA markers they found are in the same area of the brain as genetic variants linked to autism and schizophrenia. That means, say the authors of the paper in the Lancet, that ADHD would be better classified as a neurodevelopmental disorder than a behavioural problem.

"We hope that these findings will help overcome the stigma associated with ADHD," said Professor Anita Thapar from the MRC Centre in Neuropsychiatric Genetics and Genomics at Cardiff University, one of the authors.

"Too often, people dismiss ADHD as being down to bad parenting or poor diet. As a clinician, it was clear to me that this was unlikely to be the case. Now we can say with confidence that ADHD is a genetic disease and that the brains of children with this condition develop differently to those of other children."

One in 50 children is affected by ADHD, and while it used to be thought that they grow out of it, many continue to have problems in adult life.A genetic link has been suggested for some time, but not proven. Past investigations have shown that ADHD is more likely in a child who has a parent that suffers from the disorder, and that if one twin has ADHD, the other twin has a 75% chance of also having it.

But the study has found the first direct evidence by analysing DNA samples from 366 children diagnosed with ADHD, aged five to 17, and 1,047 children without the condition. They found the children with ADHD were more likely to have certain small segments of DNA either duplicated or missing than the other children. Although this finding was limited to 16% of all the children with ADHD, they say it is highly likely the rest have other genetic variants that have not yet been identified.

The researchers point out that they have not found a single gene that is responsible for the condition, and environmental circumstances will also be part of the picture – although as yet they do not know what those are. "ADHD is a very complex disorder which will have a number of different causes. A number of different genetic factors will be involved along with other, non-genetic factors," said Dr Kate Langley, another of the authors.

The findings will not be used for diagnosing ADHD, they add, but they result in new treatments. The stimulant drugs most commonly used to control the symptoms have been around since the 1950s.ADHD support groups warmly welcomed the findings, which they said would make life easier for families.

"This is indeed extremely welcome news of clear evidence to confirm that attention-deficit/hyperactivity disorder (ADHD) is indeed a brain development disorder with closer links to autism than was previously thought," said Simon Hensby of Adders, an online information organisation.

"I hope this will be a welcome relief to the many families who have to face criticism and ridicule on a daily basis, when trying to explain the behaviour of their ADHD child. I hope also that many adults with ADHD will feel much better knowing that their condition wasn't something to do with their upbringing or diet.

"Extremely low self esteem is probably the biggest common factor in those diagnosed with ADHD, both children and adults. Now we can point to proof that it is a neurodevelopmental disorder. Let us hope that this leads to a better understanding and treatment for children and adult sufferers alike."

Sheena Crankson, who has been diagnosed with ADHD herself and whose 13-year-old son Jesse has the condition, said that people blamed her all the time. "So many parents will have been told it's them, for years, in spite of the fact that your child is struggling and their self-esteem is going down and down and your self-esteem is too," she said.

Crankson, who lives in New Maldon, Greater London, once took her son to an NHS sleep and behaviour clinic, even though, she said, "we should have been upstairs talking to the psychiatrist about ADHD". The nurse she saw "said I think most of it is your fault". Crankson added: "I felt worse by the time they'd finished than when I went in."

She is trying to get her son, who also has other problems, a diagnosis of autistic spectrum disorder because, she said, ADHD is not taken seriously enough.